FBSD: Use CK_STAILQ_FOREACH for ifaces on FBSD 12
FreeBSD 12 changed how network interfaces and network addresses are
linked together; we're supposed to use CK_STAILQ_FOREACH to traverse
them now, instead of TAILQ_FOREACH. To try to keep this change
simpler, introduce a new macro, AFS_FBSD_NET_FOREACH, which picks the
right macro to use.
Based on a commit by tcreech@tcreech.com.
Change-Id: Iab0f93701dd60dcf4237a7fbbf461019bceaeb38
Reviewed-on: https://gerrit.openafs.org/13999
Reviewed-by: Tim Creech <tcreech@tcreech.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>